Bacteriophage T7 mRNA is polyadenylated.
To determine whether the RNA of bacterial viruses is polyadenylated like bacterial mRNAs, pulse-labelled as well as the steady-state population of bacteriophage T7-specific transcripts were examined for the presence of poly(A) tracts by binding to oligo(dT) cellulose followed by hybridization with specific gene probes. Representatives of all classes of bacteriophage-specific mRNA--early, middle and late--were found to be polyadenylated. This conclusion was confirmed by screening the products of oligo(dT)-dependent cDNA synthesis. A cDNA library was prepared from RNA synthesized after bacteriophage T7 infection and the sequence of bacteriophage-specific clones was determined to define the sites of polyadenylation. About half of the clones were polyadenylated near the end of a protein-coding region, one of them at the site of post-transcriptional processing by RNase III. Other clones were polyadenylated within protein-coding regions. These observations suggest that polyadenylation occurs after the nucleolytic processing of primary transcripts and in some cases also after mRNA degradation has already begun.
Johnson
M D
MD
Boston Biomedical Research Institute, MA 02114, USA.
Popowski
J
J
Cao
G J
GJ
Shen
P
P
Sarkar
N
N
D017123:Bacteriophage T7 / Q000235:genetics*; D001483:Base Sequence; D018076:DNA, Complementary / Q000737:chemistry; D004279:DNA, Viral / Q000737:chemistry; D004926:Escherichia coli / Q000502:physiology; D007553:Isotope Labeling; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D011061:Poly A / Q000737:chemistry*; D012333:RNA, Messenger / Q000737:chemistry*; D012367:RNA, Viral / Q000737:chemistry*; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D014461:Ultracentrifugation
D018076:DNA, Complementary; D004279:DNA, Viral; D012333:RNA, Messenger; D012367:RNA, Viral; D011061:Poly A